Active solid-state devices (e.g. – transistors – solid-state diode – Thin active physical layer which is – Low workfunction layer for electron emission
Reexamination Certificate
2002-04-18
2004-09-07
Crane, Sara (Department: 2811)
Active solid-state devices (e.g., transistors, solid-state diode
Thin active physical layer which is
Low workfunction layer for electron emission
C257S014000, C313S311000, C313S34600R
Reexamination Certificate
active
06787792
ABSTRACT:
FIELD OF THE INVENTION
The invention is in the microelectronics field. The invention particularly concerns electron emitters, electron array emitters and devices incorporating these types of emitters.
BACKGROUND OF THE INVENTION
Electron emitters have a wide range of potential applicability in the microelectronics field. The controlled emissions form a basis to create a range of useful electrical and optoelectrical effects. Prior conventional emitters include spindt tip cold cathode devices, MIS (metal-insulator-semiconductor), MOS (metal-oxide-semiconductor) and MIM (metal-insulator-metal) flat emitters.
Challenges presented by spindt tip emitters include manufacturability and stability, both temporal and spatial. Emission from these devices depends upon field strength at the tip and the work function of the material making up the tip. Slight imperfections in the tip shape, topology, or surface contamination can have large effects in emission density, stability, and emitter lifetime.
Manufacturing large numbers of identical tips at the Angstrom level is difficult. Once a tip is formed it can change over the lifetime of its operation. If not operated in high vacuum conditions, emitted electrons can ionize gaseous atoms. The ionized contaminants are attracted to the spindt tip and collide with it, thereby causing damage. This damage causes a change in the topology of the surface and the tip of the emitter as well as possibly changing the composition of the material such that a change in emission current, stability, or lifetime can be seen.
Traditional flat emitters are comparably advantageous because they present a larger emission surface that can be operated in less stringent vacuum environments. (Flat emitters typically include a dielectric emission layer that responds to an electrical field created by a potential applied between an electron source and a thin metal cathode on either side of a dielectric layer.) There are many theories and proposals as to the true mechanism of emission for these devices, but the basic premise is that electrons tunnel from the junction of the source and dielectric to the conduction band of the dielectric somewhere in the dielectric layer. Once in the conduction band, the electrons are ballistically accelerated towards the thin metal cathode. The electrons then tunnel through the thin metal cathode and exit the emitter.
Drawbacks to the use of these traditional flat emitters (MIS, MOS and MIM) include lifetime stability, spatial resolution and low efficiency. The lifetime stability of these devices depends highly upon the thickness of the dielectric. The thicker the dielectric, the better the lifetime of these devices can be due to the robustness of the dielectric layer. On the other hand, thicker dielectric materials lowers the efficiency of an already inefficient material reducing the amount of beam current that can be extracted from these devices. Finally, spatial resolution is decreased for these materials due to collisions of the electrons with atoms while passing through the insulator layer and the thin metal electrode layer. This disrupts chemical bonds (reducing lifetime) and scatters the electrons reducing the ease with which they may be focused.
SUMMARY OF THE INVENTION
An emitter includes an electron supply layer, a dielectric layer on the electron supply layer defining an emission area, and a filled zeolite emission layer within the defined emission area and in contact with the electron supply layer. The filled zeolite emission layer holds a semiconductor material within the cage of the zeolite.
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Novet Thomas
Schut David M.
Crane Sara
Hewlett--Packard Development Company, L.P.
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